Method for transmitting the pdcch signal

ABSTRACT

The present invention provides a method for transmitting a PDCCH (physical downlink control channel) signal, when the number of available resource blocks of the downlink bandwidth in a radio frame is less than or equal to k, 2 symbols are fixedly used to transmit the physical downlink control channel, wherein k is a natural number. The present invention further provides another method for transmitting a PDCCH signal. In a TDD Long Term Evolution system, when the number of available resource blocks of the downlink bandwidth in a radio frame is less than or equal to k and the uplink/downlink switching period is 10 ms, the transmitting end selects 2, 3 or 4 symbols to transmit the PDCCH signal in subframe  6.  With the transmission method of the PDCCH signal provided in the present invention, the utilization efficiency of the system resources and the transmission performance of PDCCH can be improved.

TECHNICAL FIELD

The present invention relates to channel transmission in the filed ofcommunication, and in particular, to a method for transmitting aphysical downlink control channel (PDCCH) signal.

BACKGROUND ART

A frame structure of the TDD (time division duplex) mode in an LTE (LongTerm Evolution) system is shown in FIG. 1. In this frame structure, aradio frame of 10 ms is divided into two half-frames; each half-frame isdivided into 10 time slots, each of which has a length of 0.5 ms, andtwo time slots form a subframe of 1 ms. A radio frame includes 10subframes (numbered from 0 to 9), and a radio frame includes 20 timeslots (numbered from 0 to 19). As for a normal cyclic prefix (CP) with alength of 5.21us and 4.69us, a time slot includes 7 uplink/downlinksymbols, each of which has a length of 66.7us, wherein the length of thecyclic prefix of the first symbol is 5.21us, and the length of thecyclic prefix of the other six symbols is 4.69us; as for an extendedcyclic prefix with a length of 16.67us, a time slot includes 6uplink/downlink symbols. Additionally, in this frame structure, thefeatures of the configuration of the subframe are as follows:

Subframe 0 and subframe 5 are always reserved for downlink transmission;

Supporting 5 ms and 10 ms downlink-to-uplink switch-point periodicity;

Subframe 1 and subframe 6 are special subframes and are used to transmit3 special time slots: DwPTS (Downlink Pilot Time Slot), GP (GuardPeriod) and UpPTS (Uplink Pilot Time Slot), wherein,

DwPTS is used for downlink transmission and includes at least 3 OFDM(Orthogonal Frequency Division Multiplexing) symbols;

GP is the guard period and does not transmit any data;

UpPTS is used for uplink transmission and includes at least 2 symbolsfor transmitting PRACH (Physical Random Access Channel).

In case of 5 ms downlink-to-uplink switch-point periodicity, subframe 2and subframe 6 are fixedly used for uplink transmission;

In case of 10 ms downlink-to-uplink switch-point periodicity, DwPTSexists in the two half-frames, GP and UpPTS exist in the firsthalf-frame, the DwPTS duration in the second half-frame is 1 ms,subframe 2 is used for uplink transmission, and subframe 7 to subframe 9are used for downlink transmission;

P-SCH (Primary-Synchronization) is transmitted on the third OFDM symbolof DwPTS; S-SCH (Secondary-Synchronization) is transmitted on the lastOFDM symbol of time slot 1 and time slot 11;

The present protocol specifies that in a TDD system, the number ofsymbols in subframe 1 and subframe 6 for transmitting physical downlinkcontrol channel signals is 1 or 2. Herein, the signal carried on thechannel is directly called as the channel signal.

A radio frame in a FDD (frequency division duplex) system also includes2 half-frames, wherein each half-frame includes 5 subframes, and eachsubframe includes two time slots. However, since it is a frequencydivision system, there is no downlink-to-uplink switch-point or specialsubframes such as subframe 1 and subframe 6 in a TDD system.

At present, when there is no physical downlink shared channel in a MBSFN(Multiple Broadcast Single Frequency Network) subframe, there is nophysical downlink control channel in this subframe either. When there isa physical downlink shared channel in a MBSFN subframe, the number ofsymbols in the subframe for transmitting physical downlink controlchannel signals is 1 or 2.

As for other normal subframes (referring to normal subframes in TDD andFDD systems), when the number of available resource blocks of thedownlink bandwidth in a radio frame is less than or equal to k (k=10),the number of symbols for transmitting physical downlink control channelsignals is 2, 3, or 4; in other cases, the number of symbols fortransmitting physical downlink control channel signals is 1, 2, or 3.

At present, the number of symbols for transmitting physical downlinkcontrol channel signals is indicated by PCFICH (Physical Control FormatIndicator Channel) in the subframe. PCFICH is transmitted on the firstsymbol of the subframe, and occupies 4 Resource element groups (REG) onthe frequency domain. However, the transmission of PCFICH will decreasethe utilization efficiency of the system resources, and reduce availablePDCCH resources, thus affecting the performance of the PDCCH.

Additionally, in TDD system, the existing protocol specifies that whenthe number of available resource blocks of the downlink bandwidth isless than or equal to k (k=10) and the downlink-to-uplink switch-pointperiod is 10 ms, the number of symbols in subframe 6 for transmittingphysical downlink control channel signals can only be 2, while thenumber of symbols in other normal frames for transmitting physicaldownlink control channel signals is 2, 3 or 4, in such a case, the cellcoverage supported by subframe 6 is lower than that supported by othersubframes, thus causing a degradation of performance of the system. Whenthe number of available resource blocks of the downlink bandwidth isgreater than k (k=10) and the downlink-to-uplink switch-point period is10 ms, the number of symbols in subframe 6 for transmitting physicaldownlink control channel signals is at most 2.

SUMMARY OF THE INVENTION

The technical problem to be solved in the present invention is toprovide a method for transmitting a physical downlink control channelsignal to improve utilization efficiency of the system resources and thetransmission performance of the physical downlink control channel.

In order to solve the above technical problem, the present inventionprovides a method for transmitting a physical downlink control channelsignal, comprising:

when the number of available resource blocks of the downlink bandwidthin a radio frame is less than or equal to k, fixedly using 2 symbols totransmit the physical downlink control channel signal, wherein k is anatural number.

Furthermore, the method is also characterized in that:

the transmitting end uses the first symbol and the second symbol of thesubframe to transmit the physical downlink control channel signal.

Furthermore, the method is also characterized in that:

the transmitting end does not set any physical control format indicatorchannel in the subframe.

Furthermore, the method is also characterized in that:

the subframe is subframe 1 and subframe 6 in a frame structure used in aLong Term Evolution (LTE) system, in the Time Division Duplex mode,k=10; or the subframe is a Multiple Broadcast Single Frequency Networksubframe in a frame structure used in an LTE system in the FrequencyDivision Duplex mode, k=10.

Furthermore, the method is also characterized in that:

the receiving end receives the physical downlink control channel signalbased on situations of the two symbols according to related downlinkcontrol signaling, when judging that the number of available resourceblocks of the downlink bandwidth is less than or equal to 10.

The method also provides a method for transmitting a physical downlinkcontrol channel signal, comprising:

when the number of available resource blocks of the downlink bandwidthin a radio frame is less than or equal to k, the transmitting end doesnot set any physical control format indicator channel in the subframe;the transmitting end selects 1 or 2 symbols to transmit the physicaldownlink control channel signal, wherein k is a natural number.

Furthermore, the method is also characterized in that:

the transmitting end uses the first symbol of the subframe, or the firstsymbol and the second symbol of the subframe to transmit the physicaldownlink control channel signal.

Furthermore, the method is also characterized in that:

the subframe is subframe 1 and subframe 6 in a frame structure used in aLong Term Evolution (LTE) system, in Time Division Duplex mode, k=10; or

the subframe is a Multiple Broadcast Single Frequency Network subframein a frame structure used in a Long Term Evolution system in theFrequency Division Duplex mode, k=10.

Furthermore, the method is also characterized in that:

the receiving end receives the physical downlink control channel signalfirstly based on the situation of one symbol by way of blind detectionaccording to related downlink control signaling, when judging that thenumber of available resource blocks of the downlink bandwidth is lessthan or equal to 10; if the receiving end does not succeed, it receivesthe physical downlink control channel signal based on situations of twosymbols.

The method also provides a method for transmitting a physical downlinkcontrol channel signal, comprising:

in the LTE system in TDD mode, when the number of available resourceblocks of the downlink bandwidth in a radio frame is less than or equalto k and the downlink-to-uplink switch-point period is 10 ms, thetransmitting end selects 2, 3 or 4 symbols in subframe 6 to transmit thephysical downlink control channel signal, wherein k is a natural number.

Furthermore, the method is also characterized in that:

the transmitting end selects the first and second symbols, or the first,second and fourth symbols, or the first, second, fourth and fifthsymbols in subframe 6 to transmit the physical downlink control channelsignal.

Furthermore, the method is also characterized in that:

when the number of available resource blocks of the downlink bandwidthin a radio frame is greater than k and the downlink-to-uplinkswitch-point period is 10 ms, the transmitting end selects 1, 2 or 3symbols in subframe 6 to transmit the physical downlink control channelsignal, wherein k is a natural number.

Furthermore, the method is also characterized in that:

when the number of available resource blocks of the downlink bandwidthin a radio frame is greater than k, the transmitting end selects thefirst symbol, or the first and second symbols, or the first, second andfourth symbols in subframe 6 to transmit the physical downlink controlchannel signal.

Furthermore, the method is also characterized in that: k=10.

The present invention also provides a method for transmitting a physicaldownlink control channel signal, comprising:

in an LTE system in TDD mode, when the number of available resourceblocks of the downlink bandwidth in a radio frame is less than or equalto k, the downlink-to-uplink switch-point period is 5 ms and a ratio ofthe number of downlink time slots to the number of uplink time slots inthe radio frame is 1:3, the transmitting end selects n symbols in anormal subframe to transmit the physical downlink control channelsignal, wherein n is 2, 3, 4 or 5, and k is a natural number.

Furthermore, the method is also characterized in that: k=10.

The transmission method of the PDCCH signal provided in the presentinvention solves the problems of wasting of resource and the degradationof the transmission performance of the PDCCH in special scenarios, andimproves the utilization efficiency of the system resources and thetransmission performance of PDCCH.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a frame structure in an LTE TDD system.

PREFERRED EMBODIMENTS OF THE INVENTION

Some specific examples of the method according to the present inventionare provided below with reference to the figure for better understandingthe present invention.

The First Embodiment

When the number of available resource blocks of the downlink bandwidthin a radio frame is less than or equal to 10 (or other specifiedvalues):

In a TDD system, the transmitting end does not set any physical controlformat indicator channel in subframe 1 and subframe 6, the resources fortransmitting physical control format indicator channel signals are usedto transmit physical downlink control channel signals; the number ofsymbols for transmitting physical downlink control channel signals is 2,for example the first and second symbols of subframe 1 and subframe 6are used.

In a FDD system, when there is a physical downlink shared channel in aMBSFN subframe for transmission, the transmitting end does not set anyphysical control format indicator channel in the subframe, the resourcesfor transmitting physical control format indicator channel signals areused to transmit physical downlink control channel signals; the numberof symbols for transmitting physical downlink control channel signals is2, for example the first and second symbols of the subframe are used.

In the above TDD and FDD systems, since when the number of availableresource blocks of the downlink bandwidth is less than or equal to 10,the number of symbols in the above subframes for transmitting physicaldownlink control channel signals can only be 2, the receiving endreceives the physical downlink control channel signals based onsituations of two symbols according to related downlink controlsignaling, when judging that the number of downlink bandwidth availableresource blocks is less than or equal to 10. There is no limit in thepresent invention on whether to set a physical control format indicatorchannel, so a physical control format indicator channel may also be set,but in any case 2 symbols are fixedly used for transmitting physicaldownlink control channel signals.

The Second Embodiment

When the number of available resource blocks of the downlink bandwidthin a radio frame is less than or equal to 10:

in a TDD system, the transmitting end does not set any physical controlformat indicator channel in subframe 1 and subframe 6, the resources fortransmitting physical control format indicator channel signals are usedto transmit physical downlink control channel signals, and the number ofsymbols for transmitting physical downlink control channel signals is 1or 2, for example the first symbol or the first and second symbols ofsubframe 1 and subframe 6.

In a FDD system, when there is a physical downlink shared channel in aMBSFN subframe for transmission, the transmitting end does not set anyphysical control format indicator channel in the subframe, the resourcesfor transmitting physical control format indicator channel signals areused to transmit physical downlink control channel signals, and thenumber of symbols for transmitting physical downlink control channelsignals is 1 or 2, for example the first symbol or the first and secondsymbols of the subframe.

In the above TDD and FDD systems, the receiving end receives thephysical downlink control channel signal firstly based on the situationof one symbol by way of blind detection according to related downlinkcontrol signaling, when judging that the number of available resourceblocks of the downlink bandwidth is less than or equal to 10, i.e.,adopting decoding and demodulation corresponding to this situation; Ifthe receiving end does not succeed, it receives the physical downlinkcontrol channel signal based on situations of two symbols.

Since no physical control format indicator channel is set in thespecific subframes in the above two embodiments, the utilizationefficiency of the system resources can be improved and the number ofsymbols for transmitting physical downlink control channel signals isincreased.

The Third Embodiment

In a TDD system, when the number of available resource blocks of thedownlink bandwidth in a radio frame is less than or equal to 10 and thedownlink-to-uplink switch-point period is 10 ms, the transmitting enduses 2, 3 or 4 symbols in subframe 6 to transmit the physical downlinkcontrol channel signals, for example, the first and second symbols, orthe first, second and fourth symbols, or the first, second, fourth andfifth symbols in the subframe are used.

In a TDD system, when the number of available resource blocks of thedownlink bandwidth in a radio frame is greater than 10 and thedownlink-to-uplink switch-point period is 10 ms, the transmitting enduses 1, 2 or 3 symbols in subframe 6 to transmit the physical downlinkcontrol channel signals, for example, the first symbol, or the first andsecond symbols, or the first, second and fourth symbols in the subframeare used.

In the above two technical schemes, the use of the specific number ofsymbols in subframe 6 for transmitting physical downlink control channelsignals may be determined according to the cell range to be coveredcurrently; more symbols can be used when the transmitting end isrelatively far from the base station. In this way, the problems that thecell coverage supported by subframe 6 is lower than those supported byother subframes and the deterioration of the system performance can beavoided.

The Fourth Embodiment

In a TDD system, when the number of available resource blocks of thedownlink bandwidth is less than or equal to 10, the downlink-to-uplinkswitch-point period is 5 ms and a ratio of the number of downlink timeslots to the number of uplink time slots in the radio frame is 1:3,since in this case one downlink subframe has to transmit relatedresource distribution control signaling of a plurality of uplinksubframes and the number of symbols may not be sufficient, thetransmitting end in this case according to this embodiment uses thefirst n symbols in a normal subframe (subframes other than subframe 1and subframe 6) to transmit the physical downlink control channelsignals, wherein n may be 2, 3, 4 or 5.

The above embodiments are only preferred embodiments of the presentinvention, and are not intended to limit the present invention. For aperson having ordinary skill in the art, the present invention may havevarious modifications and variations. All modifications, equivalentreplacements, improvements, etc. made to the present invention withinthe spirit and principle of the present invention shall fall into thescope of the claims of the present invention.

INDUSTRIAL APPLICABILITY

The present invention provides a method for transmitting physicaldownlink control channel (PDCCH), solves the problems of the wasting ofresources and the degradation of the transmission performance of thePDCCH in special scenes, and improves the utilization efficiency of thesystem resources and the transmission performance of the PDCCH.

1. A method for transmitting a physical downlink control channel signal,comprising: when the number of available resource blocks of the downlinkbandwidth in a radio frame is less than or equal to k, fixedly using 2symbols to transmit the physical downlink control channel signal,wherein k is a natural number.
 2. The method according to claim 1,wherein: the transmitting end uses the first symbol and the secondsymbol of the subframe to transmit the physical downlink control channelsignal.
 3. The method according to claim 2, wherein, the transmittingend does not set any physical control format indicator channel in thesubframe.
 4. The method according to claim 1, wherein: the subframe issubframe 1 and subframe 6 in a frame structure used in a Long TermEvolution (LTE) system in the Time Division Duplex mode, k=10; or thesubframe is a Multiple Broadcast Single Frequency Network subframe in aframe structure used in an LTE system in the Frequency Division Duplexmode, k=10.
 5. The method according to claim 4, wherein: the receivingend receives the physical downlink control channel signal based onsituations of the two symbols according to related downlink controlsignaling, for example, when judging that the number of availableresource blocks of the downlink bandwidth is less than or equal to 10.6. A method for transmitting a physical downlink control channel signal,comprising: when the number of available resource blocks of the downlinkbandwidth in a radio frame is less than or equal to k, the transmittingend does not set any physical control format indicator channel in thesubframe, and selects 1 or 2 symbols to transmit the physical downlinkcontrol channel signal, wherein k is a natural number.
 7. The methodaccording to claim 6, wherein: the transmitting end uses the firstsymbol of the subframe, or the first symbol and the second symbol of thesubframe to transmit the physical downlink control channel signal. 8.The method according to claim 6, wherein: the subframe is subframe 1 andsubframe 6 in a frame structure used in a Long Term Evolution (LTE)system in the Time Division Duplex mode, k=10; or the subframe is aMultiple Broadcast Single Frequency Network subframe in a framestructure used in an LTE system in the Frequency Division Duplex mode,k=10.
 9. The method according to claim 8, wherein: the receiving endreceives the physical downlink control channel signal firstly based onthe situation of one symbol by way of blind detection according torelated downlink control signaling, when judging that the number ofavailable resource blocks of the downlink bandwidth is less than orequal to 10; if the receiving end does not succeed, it receives thephysical downlink control channel signal based on situations of twosymbols.
 10. A method for transmitting a physical downlink controlchannel signal, comprising: in a Long Term Evolution (LTE) system withthe Time Division Duplex mode, when the number of available resourceblocks of the downlink bandwidth in a radio frame is less than or equalto k and the downlink-to-uplink switch-point period is 10 ms, thetransmitting end selecting 2, 3 or 4 symbols on subframe 6 to transmitthe physical downlink control channel signal, wherein k is a naturalnumber.
 11. The method according to claim 10, wherein: the transmittingend selects the first and second symbols, or the first, second andfourth symbols, or the first, second, fourth and fifth symbols insubframe 6 to transmit the physical downlink control channel signal. 12.The method according to claim 10, wherein: when the number of availableresource blocks of the downlink bandwidth in a radio frame is greaterthan k and the downlink-to-uplink switch-point period is 10 ms, thetransmitting end selects 1, 2 or 3 symbols in subframe 6 to transmit thephysical downlink control channel signal, wherein k is a natural number.13. The method according to claim 12, wherein: the transmitting endselects the first symbol, or the first and second symbols, or the first,second and fourth symbols in subframe to transmit the physical downlinkcontrol channel signal.
 14. The method according to claim 10, wherein,k=10.
 15. A method for transmitting a physical downlink control channelsignal, comprising: in a Long Term Evolution system with Time DivisionDuplex mode, when the number of available resource blocks of thedownlink bandwidth in a radio frame is less than or equal to k, thedownlink-to-uplink switch-point period is 5 ms and a ratio of the numberof downlink time slots to the number of uplink time slots in the radioframe is 1:3, the transmitting end selects n symbols in a normalsubframe to transmit the physical downlink control channel signal,wherein n is 2, 3, 4 or 5, and k is a natural number.
 16. The methodaccording to claim 15, wherein, k=10.
 17. The method according to claim2, wherein: the subframe is subframe 1 and subframe 6 in a framestructure used in a Long Term Evolution (LTE) system in the TimeDivision Duplex mode, k=10; or the subframe is a Multiple BroadcastSingle Frequency Network subframe in a frame structure used in an LTEsystem in the Frequency Division Duplex mode, k=10.
 18. The methodaccording to claim 3, wherein: the subframe is subframe 1 and subframe 6in a frame structure used in a Long Term Evolution (LTE) system in theTime Division Duplex mode, k=10; or the subframe is a Multiple BroadcastSingle Frequency Network subframe in a frame structure used in an LTEsystem in the Frequency Division Duplex mode, k=10.
 19. The methodaccording to claim 7, wherein: the subframe is subframe 1 and subframe 6in a frame structure used in a Long Term Evolution (LTE) system in theTime Division Duplex mode, k=10; or the subframe is a Multiple BroadcastSingle Frequency Network subframe in a frame structure used in an LTEsystem in the Frequency Division Duplex mode, k=10.
 20. The methodaccording to any of claim 12, wherein, k=10.